Piezoelectric percussion fuze

ABSTRACT

Piezoelectric percussion fuze for projectiles wherein mechanical impact energy is converted, in a piezoelectric transducer, into an electric voltage for the detonation of a primer charge, characterized in that the piezoelectric transducer is connected to the primer charge via a semiconductor element exhibiting a threshold value breakdown characteristic.

United States Patent Bendler et al.

PIEZOELECTRIC PERCUSSION FUZE Inventors: Hellmut Bendler, Nurnberg; Uwe

Brede, Schweig; Heinz Gawlick, Furth; Hans-Heinrich Rudolph, Egersdorf, all of Germany Dynamit Nobel Aktiengesellschaft, Troisdorf, Germany Filed: June 1, 1970 Appl. N0.: 42,063

Assignee:

[30] Foreign Application Priority Data May 30, 1969 Germany 1927519 US. Cl 102/70.2 R, 102/702 I Int. Cl...... F42c 11/02, F42c l/04, F420 19/06 Field of Search 102/28, 70.2 R, 70.2 G,

References Cited UNITED STATES PATENTS 7/1965 Meade 102/702 GA Jan. 15, 1974 3,389,275 6/1968 Brothers 102/702 R 3,397,329 8/1968 Riedel 3,337,758 8/1967 Brothers 102/702 R 3,098,163 7/1963 Bliss 102/702 GA FOREIGN PATENTS OR APPLICATIONS 1,527,283 4/1968 France 102/702 A Primary ExaminerBenjamin A. Borchelt Assistant Examiner-Thomas H. Webb Attorney-Craig, Antonelli, Stewart and Hill [57] ABSTRACT Piezoelectric percussion fuze for projectiles wherein mechanical impact energy is converted, in a piezoelectric transducer, into an electric voltage for the detonation of a primer charge, characterized in that the piezoelectric transducer is connected to the primer charge via a semiconductor element exhibiting a threshold value breakdown characteristic.

12 Claims, 2 Drawing Figures PMENTEDJMHSHN SIB-SL292 HGI FIG. 2 2 6 PRIMER J I v INERTIA/ CONTACT/ MASS PLATE CHARGE PIEZOELECTRIC PERCUSSION FUZE This invention relates to a piezoelectric percussion fuze for projectiles, wherein mechanical percussion energy is converted, in a piezoelectric transducer, into an electric voltage for the detonation of an explosive charge.

Percussion fuzes are known wherein the electric voltage required for the initiation of the explosive charge is supplied by a piezoelectric transducer. An electric voltage is produced in the piezo crystal, due to the mechanical impingement impulse of the projectile, which voltage is sufficient to ignite the detonator charge. In this connection, it is a disadvantage that the percussion fuzes provide mechanically movable parts which must execute an electric switching function at the instant of impact. For this reason, the function of the percussion fuze is extensively dependent on the direction of the impact impulse or on the impingement angle of the projectile, and the functional reliability is strongly impaired, due to the fact that mechanical parts are susceptible to trouble.

It is the object of the present invention to provide a piezoelectric percussion fuze of the type mentioned in the foregoing, the detonating reliability of which is increased as compared to conventional fuzes, and the initiating behavior of which is substantially entirely inde pendent of the direction of the impact force. This objective is attained, in accordance with the invention, by connecting the piezoelectric transducer to the detonator charge by way of an electric semiconductor element having a threshold value or clipping characteristic.

By the incorporation of the electric semiconductor element into the fuze combination, the objective is achieved that the voltage at the piezo crystal is not reduced by the low-ohmic primer charge path so long as the switching voltage level has not been reached; thus, only when the necessary ignition voltage is reached will a sudden switching step take place. In order to perform the voltage-dependent switching operation, no movable components are necessary, so that the entire percussion fuze can consist of individual parts fixedly installed in a housing, which parts need merely execute electrical functions. In addition to the advantage of high safety in operation, there is also the possiblity of relatively simple mass production of this item.

In an advantageous embodiment of the invention, the insulation surrounding the piezoelectric transducer and an inertia mass simultaneously constitutes the dielectric medium of a capacitor formed between the inertia mass and the housing of the percussion fuze. During the construction of the percussion fuze, the capacitance of this capacitor can be extensively predetermined, and preferably amounts to about 1000 pf. By suitably selecting this capacitance, the piezo crystal and the semiconductor element can be coordinated to each other with respect to their power and other characteristics.

As the semiconductor element, a four-layer diode is preferably employed. Four-layer diodes exhibit a pronounced threshold characteristic, i.e., they provide a high impedance at small input voltages and become suddenly low impedance as the input voltage reaches a certain threshold value. In this manner, the effect is obtained that input voltages below the switching thresh old do not affect the detonator charge; rather, the latter is ignited only when the impact or percussion energy has built up the detonating voltage to the threshold level of the diode predetermined by the desired switching voltage. Preferably, four-layer diodes having a switching threshold of about 500 volts are employed; however, depending on the field of application and the detonating conditions, it is also possible to utilize combined structural components having a similar switching behavior.

It is an object of the present invention to provide a piezoelectric percussion fuze which eliminates or otherwise avoids the disadvantages inherent in known devices of a similar nature.

It is an object of the present invention to provide a piezoelectric percussion fuze having no mechanically movable parts for executing the electric switching function at the instant of impact.

It is a further object of the present invention to provide a piezoelectric percussion fuze having a high functional reliability.

These and other objects, features and advantages of the present invention will become more apparent from the following detailed description thereof when taken in conjunction with the accompanying drawing, wherein:

FIG. 1 shows a piezoelectric percussion fuze in longitudinal section, and

FIG. 2 shows a schematic circuit diagram of the percussion fuze according to FIG. 1.

Looking first to FIG. I, the individual parts of the fuze are accommodated in a cylindrical electrically conductive detonator housing 4, one front end of which is sealed. The closed front end serves as an abutment for a piezoelectric chip 1; adjacent. to the latter, an inertia mass 2 made of a metallic material is disposed. The piezo pellet l, as well as the detonator block 2 are surrounded by a cylindrical insulating layer, this layer, as well as the other insulating parts being provided with reference numeral 3. The disk-shaped four-layer diode 5 follows the inertia mass 2; this diode is insulated with respect to the detonator housing 4, but is in electrical contact on one side with the inertia mass 2 and on the other side with a metallic contact plate 6. The primer charge 8 is provided adjacent the metal plate 6, which latter is likewise insulated with respect to the housing 4. The primer charge is surrounded. by a tubular spacer sleeve 7 which is in electrical contact with the housing 4. The unit formed by the contact plate 6, the insulation 3, the spacer sleeve 7, as well as the electric primer charge 8 is called the detonator 9.

In FIG. 2, the equivalent-circuit diagram of the fuze is illustrated. The circuit elements are, in each case, provided with the reference numeral designations for those components of the fuze in FIG. 1 to which they correspond directly. It can be seen that the piezo crystal 1 is connected, at one end, to the detonator housing 4 (ground) and, at the other end, via the very lowohmic inertia mass 2, with the four-layer diode 5. The junction point is connected to ground via the capacitor 42 formed between the detonator housing 4 and the inertia mass 2. Likewise, a capacitance 46 is disposed between the junction point of the contact plate 6 with the primer charge 8, and the detonator housing 4.

From the sectional view of FIG. 1, as well as from the equivalent electric circuit diagram of FIG. 2, it can be seen that an electric voltage built up at the piezo crystal 1 due to an applied impact stress is transmitted to the primer charge 8 only when the value of this voltage exceeds the switching or threshold voltage of the fourlayer diode 5 interposed therebetween. Accordingly, the four-layer diode 5 must be exactly adjusted to the dimensions and properties of the primer charge, as well as the remaining parts of the percussion fuze. Due to the capacitances, in conjunction with the four-layer diode, a good adaptation of power can be achieved so that it is unnecessary, as was customary heretofore, to employ high-ohmic detonator elements which are sensitive to electrostatic charging. In the device of the present invention, detonating elements having resis tance values of between, for example, and 200 ohms can be utilized.

The nature, the hardness, and the density, as well as the configuration of the abutment against which the piezo crystal 1 is pressed upon impact are of importance for the structure of the percussion fuze, as well as the dimensioning of the four-layer diode and the other components. The range of application of the fuze is determined by the velocity of the projectile, the shock wave propagation time in the projectile, and the ignition period of fuze. Experiments have shown that the percussion fuze of this invention can be successfully employed in conventional projectiles, for example in hollow-charge projectiles with a nose cap, within wide velocity ranges.

Apart from employing a four-layer diode as the semiconductor component having a threshold value characteristic, it is also possible to utilize other suitable electronic circuit components, such as, for example, Zener diodes, or the like, if they meet the proposed requirements with respect to the switching threshold. By the exclusive use of stationary components which can be firmly compacted within a common building block, high reliability and safety, as well as an extensive independence with respect to the direction of the impact impulse, are achieved.

Although the present invention has been described with reference to but a single embodiment, it is to be understood that the scope of the invention is not limited to the specific details thereof, but is susceptible of numerous changes and modifications as would be apparent to one with normal skill in the pertinent technology.

What we claim is:

l. Piezoelectric percussion fuze for projectiles comprising a housing containing an explosive charge ignitable in response to an applied electric voltage, an inertia mass within said housing, a piezoelectric transducer arranged between an abutment means of said housing and said inertia mass, said piezoelectric transducer being responsive to the force of the inertia mass for providing an electrical voltage for the initiation of said explosive charge upon impact of the projectile, a switching means responsive to the electrical voltage provided by said transducer for controlling the application of the voltage to said explosive charge, said switching means having a threshold characteristic which blocks the application of all voltages to said explosive charge below a predetermined threshold value, said switching means including a semiconductor element arranged for abutment at one portion thereof with said inertia mass such that said inertia mass electrically connects said piezoelectric transducer and said semiconductor element, said semiconductor element providing an electrical voltage upon exceeding said predetermined threshold value to a contact plate electrically connected thereto, said contact plate applying the voltage generated by said piezoelectric transducer to said explosive charge, said piezoelectric transducer, said inertial mass, said contact plate and said explosive charge being arranged in compact relation within said housing to form a common structural unit.

2. A percussion fuze as defined in claim 1, wherein said housing electrically connects said explosive charge to one side of said piezoelectric transducer.

3. A percussion fuze according to claim 1, further comprising insulation means interposed between said housing and said inertia mass for forming a capacitance therebetween.

4. A percussion fuze as defined in claim 3, wherein the capacitance formed by said insulation means is approximately 1000 pf.

5. A percussion fuze as defined in claim 2, further comprising insulation means between said inertia mass and said housing and between said contact plate and said housing so as to form a capacitance to said housing on either side of said semiconductor element.

6. A percussion fuze as defined in claim 1, wherein said semiconductor element is a four-layer diode.

7. A percussion fuze according to claim 1, wherein the predetermined threshold value of the semiconductor element is approximately 500 volts.

8. A percussion fuze as defined in claim 2, wherein said inertia mass, contact plate, explosive charge and housing form a detonator element as electrically connected having a combined impedance of about 20-200 ohms.

9. A percussion fuze as defined in claim 1, wherein said housing of the structural unit is conductive and has a diameter of not more than 10 mm. and a length of no more than 50 mm.

10. A percussion fuze as defined in claim 1, wherein said semiconductor element is disc-shaped and is arranged in abutting relation at one side thereof with said inertia mass and being arranged in abutting relation with said contact plate at the other side thereof, said contact plate being in electrical contact with said explosive charge.

11. A percussion fuze as defined in claim 1, wherein said piezoelectric transducer, said inertia mass, said semiconductor element, said contact plate and said explosive charge are arranged in alignment and in abutting relation within said housing.

12. A percussion fuze as defined in claim 1, wherein said semiconductor element is disc-shaped. 

1. Piezoelectric percussion fuze for projectiles comprising a housing containing an explosive charge ignitable in response to an applied electric voltage, an inertia mass within said housing, a piezoelectric transducer arranged between an abutment means of said housing and said inertia mass, said piezoelectric transducer being responsive to the force of the inertia mass for providing an electrical voltage for the initiation of said explosive charge upon impact of the projectile, a switching means responsive to the electrical voltage provided by said transducer for controlling the application of the voltage to said explosive charge, said switching means having a threshold characteristic which blocks the application of all voltages to said explosive charge below a predetermined threshold value, said switching means including a semiconductor element arranged for abutment at one portion thereof with said inertia mass such that said inertia mass electrically connects said piezoelectric transducer and said semiconductor element, said semiconductor element providing an electrical voltage upon exceeding said predetermined threshold value to a contact plate electrically connected thereto, said contact plate applying the voltage generated by said piezoelectric transducer to said explosive charge, said piezoelectric transducer, said inertial mass, said contact plate and said explosive charge being arranged in compact relation within said housing to form a common structural unit.
 2. A percussion fuze as defined in claim 1, wherein said housing electrically connects said explosive charge to one side of said piezoelectric transducer.
 3. A percussion fuze according to claim 1, further comprising insulation means interposed between saId housing and said inertia mass for forming a capacitance therebetween.
 4. A percussion fuze as defined in claim 3, wherein the capacitance formed by said insulation means is approximately 1000 pf.
 5. A percussion fuze as defined in claim 2, further comprising insulation means between said inertia mass and said housing and between said contact plate and said housing so as to form a capacitance to said housing on either side of said semiconductor element.
 6. A percussion fuze as defined in claim 1, wherein said semiconductor element is a four-layer diode.
 7. A percussion fuze according to claim 1, wherein the predetermined threshold value of the semiconductor element is approximately 500 volts.
 8. A percussion fuze as defined in claim 2, wherein said inertia mass, contact plate, explosive charge and housing form a detonator element as electrically connected having a combined impedance of about 20-200 ohms.
 9. A percussion fuze as defined in claim 1, wherein said housing of the structural unit is conductive and has a diameter of not more than 10 mm. and a length of no more than 50 mm.
 10. A percussion fuze as defined in claim 1, wherein said semiconductor element is disc-shaped and is arranged in abutting relation at one side thereof with said inertia mass and being arranged in abutting relation with said contact plate at the other side thereof, said contact plate being in electrical contact with said explosive charge.
 11. A percussion fuze as defined in claim 1, wherein said piezoelectric transducer, said inertia mass, said semiconductor element, said contact plate and said explosive charge are arranged in alignment and in abutting relation within said housing.
 12. A percussion fuze as defined in claim 1, wherein said semiconductor element is disc-shaped. 